Question

The reason behind the lower atomic radius of $Ga$ as compared to $Al$ is

• A. poor screening effect of $d$-electrons for the outer electrons from increased nuclear charge
• B. increased force of attraction of increased nuclear charge on electrons
• C. increased ionisation enthalpy of $Ga$ as compared to $Al$
• D. anomalous behaviour of $Ga$

Answer 1

Answer: (A)

Presence of $10 \,d$-electrons in gallium which have poor screening effect on the outer electrons increases the force of attraction between the outermost electrons and nuclear charge resulting in decrease in atomic radius.